This invention relates to vehicular rearview mirrors and, more particularly, to vehicle mirrors incorporating apparatus to provide an information display for viewing by the vehicle driver or passengers in conjunction with viewing the rearview mirror.
In recent years, rearview mirrors for vehicles, especially those mounted inside vehicles, have included courtesy, reading or map lights, compasses, headlight dimming sensors and other instruments or controls. It has also been proposed to provide information to the driver of the vehicle by mounting warning or indicator lights, gauges, instrument readouts or the like above, around or near the rearview mirror such that the vehicle driver can view such information while looking in the direction of the rearview mirror. This enhances safety by diverting the driver's attention away from the road less frequently.
Some prior known assemblies have included warning or indicator lights mounted in the rearview mirror case around the periphery of the mirror itself. See for example Bouthors U.S. Pat. No. 4,109,235 which discloses various signal lamps and symbols above the mirrored surface and various readouts for other information below the mirrored surface, both being mounted in a specially designed mirror case. Such assemblies are expensive to manufacture because they require unique, completely redesigned mirror cases which incorporate the lights, indicators and other signaling apparatus. They also greatly enlarge the size of the mirror assembly thereby taking up a greater proportion of the forward viewing area adjacent the windshield.
Other rearview mirror assemblies are known which include warning lights or liquid crystal displays positioned directly in the mirrored surface. For example, Pastore U.S. Pat. No. 4,588,267 discloses a combination rearview mirror and clock or instrument display wherein a large circle or rectangle of the mirrored surface is removed and an instrument such as a clock, fuel gauge or warning light is positioned behind the removed area for readout through that area from the front of the mirror. When warning lights are used, relatively large sized circles are used with printed words indicating the nature of the warning placed directly on the front surface of the mirror such as "battery", "oil", or "seat belt". Such assemblies are also large and typically require redesigned rearview mirror cases. More importantly, however, the information displays provided are highly noticeable at all times on the mirror surface and are large enough to interfere with proper viewing of images in the mirror from the rear of the vehicle. Likewise, those areas in such mirrors using liquid crystal displays lack brightness and color for distinguishing different types of symbols, and are still so large that they were noticeable even when unlit to drivers when viewing the mirror surface. Therefore, these assemblies tend to interfere with proper viewing in the mirror and are less desirable from a safety standpoint.
Yet another type of information mirror provides an electroluminescent display behind a translucent or "one way" mirror coating on an interior vehicular rearview mirror. For example, Suzuki et al. U.S. Pat. No. 4,499,451 discloses a glass substrate having a second surface, thin, translucent reflective layer which reflect only a part of the light incident thereon while allowing the remainder to pass therethrough. A planar electroluminescent electrode is printed or applied to the rear surface of the translucent layer and is formed either in the shape of indicia or covered with an electrode shaped in the form of indicia. When voltage is applied, the electroluminescent layer lit up in the shape of the electrode to provide information visible through the translucent layer from the front of the mirror. While remaining inconspicuous when voltage is switched off, this assembly does require significantly large size indicia relative to the size of the mirrored surface such that proper viewing through the light inhibiting layer can be made. Such large size indicia dominate the mirrored surface when activated such that interference with vision of images in the rearview mirror to the rear of the vehicle occurs. In addition, significant control circuitry is necessary for the electroluminescent electrode including a transformer connected with the direct current vehicle electrical system.
Accordingly, the prior known information mirrors left unsolved the need for an appropriate information display which would be unnoticeable to the driver and avoid obstruction of rear vision when unlit or unactivated, be less expensive, be suitable for mass production, allow accurate, small sized indicia, and yet allow sufficient brightness and clarity to be easily visible and readable by the vehicle driver or passengers when lit or activated.